Pure gold is a term that often refers to gold that has been highly refined to remove impurities. The “purest” gold available in the market has undergone extensive processing to achieve an extremely high level of fineness. This refinement journey transforms raw gold from its natural geological settings into the gleaming metal prized for its various applications.
Defining Pure Gold
Gold purity is primarily measured in karats or by its fineness. Twenty-four karat (24K) gold is considered pure, signifying 100% gold content. However, achieving absolute 100% purity is practically impossible due to atomic-level impurities. Therefore, “pure gold” typically refers to gold with a fineness of 999.9 parts per thousand, often written as 999.9. Even higher purities, such as 999.99% (five nines fine), have been achieved by specialized refiners.
Natural Occurrences of Gold
Gold originates deep within the Earth’s crust, forming through complex geological processes. It is found in two main types of natural deposits: primary and secondary. Primary deposits, also known as lode or vein deposits, occur when gold is embedded within rock formations, often in quartz veins. This gold precipitates from hot, mineral-rich fluids that ascend into cracks and fissures in the crust.
Secondary deposits, or placer deposits, form when primary gold-bearing rocks undergo weathering and erosion. Natural forces like water, wind, and ice break down the rocks, releasing gold particles. Due to gold’s high density, these liberated particles are then transported and concentrated in riverbeds, stream channels, and alluvial fans. Gold found in secondary deposits often exhibits higher natural purity because transport and weathering processes tend to remove some alloying metals like silver.
From Mine to Market: Refining for Purity
After gold is extracted from its natural deposits, it undergoes a series of refining processes to achieve high purity. Initial steps often involve crushing the ore and using methods like cyanidation to extract crude gold, which still contains various impurities. To elevate this crude gold to its purest forms, specialized refining techniques are employed.
One common method is the Miller process, which achieves a purity of approximately 99.5%. This technique involves blowing chlorine gas through molten, impure gold. Most metal contaminants react with the chlorine to form chlorides, which either volatilize or create a low-density slag layer on top of the molten gold, allowing them to be separated. The Miller process is valued for its relative ease, speed, and cost-effectiveness in large-scale operations.
For the highest levels of purity, the Wohlwill process is utilized, capable of producing gold with 99.99% to 99.999% fineness. This electrochemical method involves placing impure gold as an anode in an electrolyte solution of hydrochloric acid and gold chloride. An electric current is then applied, causing the impure gold to dissolve and pure gold to deposit onto a cathode. While more time-consuming and expensive, the Wohlwill process is preferred for applications demanding exceptional purity, such as in electronics or investment-grade bullion.
Global Sources of Pure Gold
The purest gold available in the market primarily comes from advanced refining centers across the globe, rather than directly from a single mine. These specialized facilities receive raw gold from various mining operations worldwide and process it to meet stringent purity standards. Many major gold-producing nations, such as China, Australia, and the United States, serve as significant sources of the raw material that feeds these refining operations.
Reputable refineries employ sophisticated technology and adhere to strict quality control measures to ensure the fineness of their gold products. Organizations like the London Bullion Market Association (LBMA) set “Good Delivery” standards that specify the required fineness for investment-grade gold bars, typically 99.5% or higher. Therefore, the purest gold emerges from a combination of efficient mining, followed by precise and technologically advanced refining processes conducted by leading refiners globally.